The present invention concerns methods and apparatus for the chemical-mechanical planarization of articles such as semiconductor wafers.
Current trends in the integrated circuit (IC) industry include fabricating smaller devices having increased chip density. Reducing chip size can reduce chip manufacturing costs. In addition, devices having smaller dimensions can be advantageous because device delay can also be decreased, thereby increasing performance.
In addition, device performance can be increased by adding multiple levels of metallization. The use of multiple levels of metal interconnections allows for wider interconnect layer dimensions with shorter interconnect lengths. Because such lengths have only been possible with single level devices, a corresponding decrease in interconnect delay has been achieved. Nonetheless, as many interconnect levels are added, topography that builds up with each level can become severe. If not resolved, these topographies can adversely affect the reliability of the device.
As circuit dimensions are reduced, interconnect levels must be globally planarized to produce a reliable, high density device. Chemical mechanical planarization (CMP) is rapidly becoming the technique of choice for planarizing interlevel dielectric (ILD) layer surfaces and for delineating metal patterns in integrated circuits. See, e.g., U.S. Pat. No. 5,637,185 to Muraka et al.
In general, CMP processes involve holding or rotating a semiconductor wafer against a rotating wetted polishing surface under a controlled downward pressure. A chemical slurry containing a polishing agent, such as alumina or silica, is typically used as the abrasive medium. Additionally, the chemical slurry can contain chemical etchants for etching various surfaces of the wafer. In a typical fabrication of a device, CMP is first employed to globally planarize an ILD layer surface comprising only dielectric. Trenches and vias are subsequently formed and filled with metal by known deposition techniques. CMP is then typically used to delineate a metal pattern by removing excess metal from the ILD. See Murakara, supra.
One problem with CMP is the generation of expansive fluid streams that require handling and waste management. For example, problems may be presented by the toxicity of the slurries, of potentially metal containing slurry effluent, and of contaminated cleaning solutions used post-polishing or post-planarization. Water consumption during CMP is estimated to range from 10 to 20 gallons per processed wafer. CMP waste consists of highly toxic chemicals, and there has been little progress in finding methods of converting CMP waste to more manageable forms. See generally, xe2x80x9cChemical Mechanical Planarization Tries to Keep Upxe2x80x9d, Gorham Advanced Materials, (Mar. 2, 2000). A non-aqueous CMP polishing slurry is described in U.S. Pat. No. 5,863,307 to Zhou et al., but this slurry preferably employs carbon tetrachloride. Accordingly, there is a need for new approaches to carrying out chemical mechanical planarization, and new formulations for CMP polishing slurries.
Another problem is the potential for contamination of substrates through the use of water. Such contamination may include unwanted/unclaimed oxidation or trace ions or residual water affecting dielectric layers, expecially CVD layers, spin on layers and porous layers.
The present invention is based upon the development of CMP polishing slurries that contain carbon dioxide as a solvent and polishing slurries including carbon dioxide-philic compositions, either alone or in combination with one or more additional cosolvents, as well as methods using such slurries and, in some embodiments, carbon dioxide solvent cleaning. Inclusion of the carbon dioxide provides a solvent media that may be easily separated from other ingredients of the slurry or cleaning solvent, thereby reducing the volume of slurry or cleaning solvent for subsequent waste disposal.
According to preferred methods of the present invention, a method for the chemical mechanical planarization of a surface of an article such as a semiconductor wafer includes: providing a polishing slurry including carbon dioxide; providing a polishing pad; and contacting the polishing pad and the polishing slurry against the surface of the article (e.g., wafer) to thereby planarize the surface of the article. The contacting step can be carried out in an atmosphere comprising carbon dioxide at a pressure greater than atmospheric pressure.
The method may include the step of cleaning the surface of the article (e.g., wafer) using a carbon dioxide solvent following the contacting step.
The method may include rotating at least one of the pad and the article relative to the other. The article may be rotated in a first direction with the pad being rotated in a counter direction. The article may be held in a static position. The pad may include a continuous linear belt pad which may be linearly moved relative to the article.
The article (e.g., wafer) may be disposed in a pressure vessel during each of the steps of providing a polishing slurry, providing a polishing pad, and contacting the polishing pad and the polishing slurry against the surface of the article. The method may further include distilling at least a portion of the polishing slurry at a pressure greater than atmospheric pressure to separate the carbon dioxide from the remainder of the polishing slurry.
According to further preferred methods of the present invention, a method for the chemical mechanical planarization of a surface of an article such as a semiconductor wafer includes: providing a carbon dioxide-philic polishing slurry; providing a polishing pad; contacting the polishing pad and the polishing slurry against the surface of the article to thereby planarize the surface of the article; and cleaning the surface of the article with a solvent comprising carbon dioxide.
The contacting step may be executed in an atmosphere not including carbon dioxide in an amount exceeding common atmospheric conditions. The contacting step and the cleaning step may be executed in a common pressure vessel. The polishing slurry may include a polymer that is soluble in carbon dioxide.
According to further preferred methods of the present invention, a method for the chemical mechanical planarization of a surface of an article such as a semiconductor wafer includes: providing a carbon dioxide-philic polishing slurry; providing a polishing pad; and contacting the polishing pad and the polishing slurry against the surface of the article to thereby planarize the surface of the article. The contacting step may be executed in an atmosphere comprising carbon dioxide at a pressure greater than atmospheric pressure.
According to preferred embodiments of the present invention, an apparatus for the chemical mechanical planarization of a surface of an article such as a semiconductor wafer includes a polishing pad; a polishing slurry including carbon dioxide; and an article holding member to hold the article such that the surface of the article can be contacted with the polishing pad and the polishing slurry.
According to further preferred embodiments of the present invention, an apparatus for the chemical mechanical planarization of a surface of an article such as a semiconductor wafer includes a polishing pad; a carbon dioxide-philic polishing slurry; and an article holding member to hold the article such that the surface of the article can be contacted with the polishing pad and the polishing slurry.
A further aspect of the present invention is a CMP polishing slurry, comprising: (a) abrasive particles (e.g., from 1 to 20 percent by weight); and (b) optionally, but preferably, an etchant (e.g., from 0 or 0.1 to 50 or 70 percent by weight); and (c) carbon dioxide solvent (preferably dense carbon dioxide, and more preferably liquid carbon dioxide) (e.g., at least 20 or 30 percent by weight).
A further aspect of the present invention is a CO2-philic CMP polishing slurry, comprising: (a) abrasive particles (e.g. from 1 to 20 percent by weight); (b) etchant (e.g., from 0.1 to 50 percent by weight); (c) solvent (e.g., at least 30 percent by weight); and (d) a carbon-dioxide soluble polymer (e.g., from 1 to 20 or 30 percent by weight).
Objects of the present invention will be appreciated by those of ordinary skill in the art from a reading of the Figures and the detailed description of the preferred embodiments which follow, such description being merely illustrative of the present invention.